Field of the Invention
The present invention relates generally to improvements in interactive display systems and in particular to the identification of a bounded area in a graphic display system.
A common form of interaction with a graphic picture is for an operator to want to identify, to the application with which the operator is interacting, a particular object within the picture. This may be for one of a variety of reasons, for example to move the object in its relation to the other objects, modify or delete the object. A possible method of accomplishing this would be to identify the object by means of a command, e.g., DELETE BOLT 23. It is much more natural however for the operator to use a suitable device to actually point to the object. Typical devices are joystick, thumbwheel, trackball, or optical mouse coupled to a cursor in the display screen.
The immediate result of such a pointing is an (x, y) position on the screen. A correlation operation has then to be carried out to determine which of the objects in the picture actually passes through (or sufficiently close to) that point.
In order to do this a picture definition (display list) has to be scanned, just as if it were being drawn, but instead of actually drawing the objects defined in the list, they are each inspected to see whether they intersect a small square (for example) draw around the point of interest.
It is important that this process occurs quickly. The operator expects a rapid system response to indicate whether or not the pointing was successful. Since the operator has generally only pointed at one object out of the many in the picture, a critical performance factor is how quickly each of the remaining objects can be rejected.